1. Field of the Invention
The present invention relates to an image-pixel-signal processor used in, for example, an electronic video camera having a solid-type image sensor, and, in particular, to an image-pixel-signal processor for processing image-pixel signals derived from divided sections of an image-sensing area of a solid-type image sensor.
2. Description of the Related Art
In an electronic camera, a solid-type image sensor, such as a CCD (charge-coupled device) image sensor, is used to photoelectrically convert an optical objective image into a frame of image-pixel signals. The optical objective image is reproduced based on a video signal generated from the frame of image-pixel signals, which have been subjected to suitable processing.
Recently, there has been a demand for the reproduced image to have a higher resolution. A resolution of the reproduced image depends on a number of image-pixel signals included in one frame, which then corresponds to a number of CCD elements included in the CCD image sensor. As is well known, the CCD elements are arranged in a matrix on an image-sensing area or light-receiving area of the CCD image sensor. To obtain a reproduced image with a high resolution, the number of CCD elements must be increased. In this case, the increase in the number of CCD elements is exponential, because of the matrix arrangement of the CCD elements on the image-sensing area of the CCD image sensor.
On the other hand, a CCD image sensor, having a large number of CCD elements, produces a detrimental effect on the reading time of a frame of image-pixel signals from the CCD image sensor. To solve this problem, it is proposed that the image-sensing area of the CCD image sensor is vertically and/or horizontally divided into at least two sections; that image-pixel signals are simultaneously read from the divided sections of the image-sensing area; and that the read image-pixels are reintegrated to form a frame of image-pixel signals. Thus, the reading of the image-pixel signals from the CCD image sensor can be carried out in a short time.
Nevertheless, a boundary between two adjacent sections of the image-sensing area may be apparent on a reproduced image as a difference of luminous intensity between two image areas, corresponding to the two adjacent sections, of the reproduced image, because an average level of the image-pixel signals, derived from one of the two adjacent sections, may be different from an average level of the image-pixel signals, derived from the other section.
In particular, for example, the respective image-pixel signals, read from the two adjacent sections, are successively amplified by two amplifiers. In this case, although the amplifiers used are the same products, it cannot be ensured that the amplifiers exhibit the same amplification characteristic. Accordingly, the respective average levels, derived from the two adjacent sections, may be different from each other, and thus the boundary between the two adjacent sections of the image-sensing area may be apparent on the reproduced image as a difference of luminous intensity between the two image areas.
Also, in manufacturing a large-sized CCD image sensor having a large number of CCD elements, at least two small-sized CCD image sensors, each having a small number of CCD elements, are frequently combined with each other to construct the large-sized CCD image sensor. Of course, in this case, image-pixel signals are simultaneously read from the combined small-sized CCD image sensors, and the read image-pixel signals are reintegrated to form a frame of image-pixel signals. Similar to the above-mentioned case, a boundary between two adjacent combined CCD image sensors may be apparent on a reproduced image as a difference of luminous intensity between two image areas, corresponding to the combined small-sized CCD image sensors, of the reproduced image, because of different characteristics between the combined CCD image sensors and different characteristics between amplifiers incorporated into the combined CCD image sensors.
Therefore, an object of the present invention is to provide an image-pixel-signal processor for processing image-pixel signals derived from divided sections of an image-sensing area of a solid-type image sensor, wherein a boundary between two adjacent sections of the image-sensing area is not apparent as a difference between luminous intensities on a reproduced image.
In accordance with a first aspect of the present invention, there is provided an image-pixel signal processor for processing image-pixel signals obtained from an image-sensing area, divided into a first section and a second section, of a solid-type image sensor. Optionally, the solid-type image sensor may be constructed by combining at least two small-sized solid-type image sensors with each other such that the image-sensing area is formed of a first section and a second section corresponding to image-sensing areas of the small-sized solid-type image sensors, respectively. The processor comprises an image-pixel signal reader, which simultaneously and correspondingly reads two respective series of image-pixel signals line by line from the first and second sections of the image-sensing area. A leading image-pixel signal, of the image-pixel signals included in each line, is farthest away from a boundary between the first and second sections, whereas a trailing image-pixel signal, of the image-pixel signals included in each line, is nearest to the boundary. The processor also comprises a regulator, which correspondingly regulates respective differences between levels of the image-pixel signals in each line derived from the first section, and the corresponding image-pixel signals in each line derived from the second section, so that a gradual reduction occurs, resulting in both levels of the trailing image-pixel signals, derived from the first and second sections, being substantially coincident with each other.
In the first aspect of the present invention, the regulator may comprise a first level-changer for changing a level of each image-pixel signal derived from the first section, a second level-changer for changing a level of each image-pixel signal derived from the second section, a first level-detector for detecting a level of the image-pixel signal outputted from the first level-changer, a second level-detector for detecting a level of the image-pixel signal outputted from the second level-changer, a calculator for calculating a differential level between the levels of the image-pixel signals outputted from the first and second level-changers, and a weight-factor multiplier for multiplying the differential level by a weight-factor, which is cyclically varied from a minimum value to a maximum value. The first and second changers correspondingly change the levels of the image-pixel signals, derived from the first and second sections, on the basis of the differential level multiplied by the cyclically-varied weight-factor, such that the regulation of the respective differences between levels of the image-pixel signals in each line derived from the first section, and the corresponding image-pixel signals in each line derived from the second section, is carried out.
Also, in the first aspect of the present invention, each of the first and second level-changers may comprise a voltage-controlled amplifier, a magnification factor of which is controlled in accordance with a variation of an inputted control voltage, the control voltage being set on the basis of the differential level multiplied by the cyclically-varied weight-factor.
In accordance with a second aspect of the present invention, there is provided an image-pixel signal processor for processing image-pixel signals obtained from an image-sensing area, vertically divided into a first section and a second section, of a solid-type image sensor, wherein a plurality of image-pixel signals is produced in a matrix on each of the first and second sections. Optionally, the solid-type image sensor may be constructed by combining at least two small-sized solid-type image sensors with each other such that the image-sensing area is formed of a first section and a second section corresponding to image-sensing areas of the small-sized solid-type image sensors, respectively, with a vertical boundary being defined between the first and second sections. The processor comprises an image-pixel signal reader, which reads respective series of image-pixel signals, from a leading line of the first and second sections of the image-sensing area, by vertically transferring the image-pixel signals in a line by line succession, and by horizontally transferring a vertically-transferred leading line of the image-pixel signals. A leading image-pixel signal of the image-pixel signals included in each line is farthest from a vertical boundary between the first and second sections, and a trailing image-pixel signal of the image-pixel signals in each line is nearest to the vertical boundary. The processor also comprises a regulator, which correspondingly regulates respective differences between levels of the image-pixel signals in each line derived from the first section, and the corresponding image-pixel signals in each line derived from the second section, so that a gradual reduction occurs, resulting in the levels of the corresponding trailing image-pixel signals, derived from the first and second sections, being substantially coincident with each other.
In the second aspect of the present invention, the regulator comprises a first level-changer for changing a level of each image-pixel signal derived from the first section, a second level-changer for changing a level of each image-pixel signal derived from the second section, a first level-detector for detecting a level of the image-pixel signal outputted from the first level-changer, a second level-detector for detecting a level of the image-pixel signal outputted from the second level-changer, a calculator for calculating a differential level between the levels of the image-pixel signals outputted from the first and second level-changers, and a weight-factor multiplier for multiplying the differential level by a weight-factor, the weight-factor being cyclically varied from a minimum value to a maximum value, in accordance with a series of clock pulses, on the basis of which the vertical transfer of the plurality of image-pixel signals is carried out in each of the first and second sections. The first and second changers correspondingly change the levels of the image-pixel signals, derived from the first and second sections, on the basis of the differential level multiplied by the cyclically-varied weight-factor, such that the regulation of the respective differences between levels of the image-pixel signals in each line derived from the first section, and the corresponding image-pixel signals in each line derived from the second section, is carried out.
In the second aspect of the present invention, the first and second level-changers may comprise a voltage-controlled amplifier, a magnification factor of which is controlled in accordance with a variation of an inputted control voltage, the inputted control voltage being set on the basis of the differential level multiplied by the cyclically-varied weight-factor.
In accordance with a third aspect of the present invention, there is provided an image-pixel signal processor for processing image-pixel signals obtained from an image-sensing area, horizontally divided into a first section and a second section, of a solid-type image sensor, wherein a plurality of image-pixel signals is produced in a matrix on each of the first and second sections. Optionally, the solid-type image sensor may be constructed by combining at least two small-sized solid-type image sensors with each other such that the image-sensing area is formed of a first section and a second section corresponding to image-sensing areas of the small-sized solid-type image sensors, respectively, with a horizontal boundary being defined between the first and second sections. The processor comprises an image-pixel signal reader, which reads respective series of image-pixel signals, from a leading line of the first and second sections of the image-sensing area, by vertically transferring the image-pixel signals in a line by line succession, and by horizontally transferring a vertically-transferred leading line of the image-pixel signals. A leading series of the image-pixel signals, being first to be horizontally transferred from the first and second sections, is farthest from a horizontal boundary between the first and second sections, and a trailing series of the image-pixel signals, being last to be horizontally transferred from the first and second sections, is nearest to the horizontal boundary. The processor also comprises a regulator, which correspondingly regulates respective differences between levels of the image-pixel signals in respective lines derived from the first section, and levels of the image-pixel signals in respective lines derived from the second section, so that a gradual reduction occurs, resulting in the levels of the corresponding trailing-line image-pixel signals, of the first and second sections, being substantially coincident with each other.
In accordance with the third aspect of the present invention, the regulator may comprise a first level-changer for changing a level of each image-pixel signal derived from the first section, a second level-changer for changing a level of each image-pixel signal derived from the second section, a first level-detector for detecting a level of the image-pixel signal outputted from the first level-changer, a second level-detector for detecting a level of the image-pixel signal outputted from the second level-changer, a calculator for calculating a differential level between the levels of the image-pixel signals outputted from the first and second level-changers, and a weight-factor multiplier for multiplying the differential level by a weight-factor, the weight-factor being cyclically varied from a minimum value to a maximum value, in accordance with a series of clock pulses, on the basis of which the horizontal transfer of the plurality of image-pixel signals is carried out for each of the first and second sections. The first and second changers correspondingly change the levels of the image-pixel signals, derived from the first and second sections, on the basis of the differential level multiplied by the cyclically-varied weight-factor, such that the regulation of the respective differences between levels of the image-pixel signals in each line derived from the first section, and the corresponding image-pixel signals in each line derived from the second section, is carried out.
In the third aspect of the present invention, each of the first and second level-changers may comprise a voltage-controlled amplifier, a magnification factor of which is controlled in accordance with a variation of an inputted control voltage, the control voltage being set on the basis of the differential level multiplied by the cyclically-varied weight-factor.